I need to successively CNC individual layers of a DXF file, so I need separate DXF for each of them only containing the specific layer.
I have a lot of trouble doing that and I could not explicitly find it in the manual.

So how can I creat dxf's from each later in a master dxf containing all the layers.

QCAD doesn't has a tool for that and this is just a kind of workaround. Without an example drawing it is also a bit of fishing in muddy water what means there is room for improvements ...

Open the dxf with the layer collection - I'll call it Alllayer.dxf
Then ...
Layer List:
1. Switch all Layer to visible,
2. Right click on the layer which has to be isolated - choose select layer.
Menu:
3. Select -> Invert Selection
4. Delete
Menu:
5. Layer -> Purge unused Layers
6. Save as: Save the dxf regarding to the choosen layer
Close the drawing (?)
7. Open the "Alllayer.dxf" again and repeat this procedure for the next layer which has to be separated.

Tip: Work first with a copy of Alllayer.dxf until you are familiar with the procedure. Just in the case that a click was faster than expected ...

So it is not so far fetched or obscure really as many users other than me need it and clearly there is a commercial interest in it too, so the question must have been asked a lot for them to create such a commercial application. To me it is duh! obvious that it is very necessary.
It is something I need constantly.
In my case I have to make reference planes that must be part of the drawing so I can manufacture in large quantity as one example. There are many more.
There is no way around it. I need to split the layers out.

What is the Qcad scripting language. Hopefully not python? That I dont want to learn. If so any other scripting language options ?